Composting bin



FIG. 1 is an upper perspective view of a composting bin showing our new design;

FIG. 2 is a lower perspective view thereof;

FIG. 3 is a front elevational view thereof, the rear elevational view being identical;

FIG. 4 is a left side elevational view thereof, the right side elevational view being identical;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The dotted lines illustrate a portion of the composting bin that form no part of the claimed design. 

CLAIM The ornamental design for a composting bin, as shown and described. 